Numerical investigation of diffraction models of microwave integrated circuits

A stripline stub on a suspended substrate is examined. The multimode scattering matrices of the two identical jumps picking up the stub are determined by projection sewing of the systems of intrinsic waves of the narrow and wide lines. The multimode scattering matrix of the stub is found by combining the scattering matrices of the two jumps with allowance for an intermediate segment of regular line with a wide conductor. Two algorithms are constructed, one of which finds the intrinsic waves of the stripline conductor (impedance version) and the other formulates the integral equation with respect to the tangential electrical field in the boundary region (admittance version). It is found that the higher harmonics in Trefftz bases have little influence on the characteristics obtained for the fundamental wave.